1. Field of the Invention
The present invention relates to improvement in a camera having camera movement correcting means.
2. Related Background Art
A camera movement in photographing is usually a vibration of 1 Hz to 10 Hz. As a basic idea of a vibration isolation apparatus allowing a photograph to be taken with no blurring even on occurrence of such a camera movement on a release of a shutter, the vibration of the camera due to the camera movement must be detected and a correcting lens must be displaced according to a detected value thereof. Accordingly, in order to take a photograph with no blurring even on occurrence of the camera movement, it is necessary to correctly detect the vibration of the camera first and to correct a change in an optical axis due to the camera movement secondly.
This detection of the vibration (camera movement) can be performed, in principle, by mounting on the camera a detection sensor for detecting acceleration, angular acceleration, angular velocity, angular displacement and so on and camera movement correcting means having a calculation portion for appropriately calculating output thereof to correct the camera movement. And based on this detection information, the image blurring is controlled by driving the camera movement correcting means for changing a photographing optical axis.
In such a prevention system, a desired vibration isolation effect can no longer be obtained in the case where a drive amount of the camera movement correcting means corresponding to a camera movement amount detected by camera movement detection means exceeds a drive threshold amount, since the camera movement correcting means can no longer follow a displacement amount necessary for camera movement correction. As for this problem, Japanese Patent Application Laid-Open No. 06-347856 discloses the camera which finishes exposure when the camera movement exceeding the drive threshold amount of the camera movement correcting means is detected during photographing and elapse of time from start of the exposure is within a predetermined value to a proper exposure value.
However, in the case of a system, such as the vibration isolation system of a compact camera required to be small-sized, of which drive amount of the camera movement correcting means does not have sufficient allowance, performance of the above exposure control in the past renders it more frequent to exceed the drive threshold amount of the camera movement correcting means. Accordingly, on performing the exposure control of the above proposal wherein the exposure is immediately finished if it exceeds the drive threshold amount of the camera movement correcting means in a state of having finished the exposure within a predetermined value to the proper exposure value, there is a possibility that there may frequently arise scenes of so called insufficient exposure in which an exposure tolerance limit can be secured but the desired exposure value cannot be reached or many scenes in which the exposure tolerance limit is reached but the camera movement occurs.
A first object of the present invention is to provide a camera capable of expanding an area for obtaining a vibration isolation effect.
A second object of the present invention is to provide a camera capable of expanding an area for obtaining a vibration isolation effect and an area for obtaining a proper exposure value so as to allow a photographing range for a photographer to obtain an intended photograph to be expanded.
And the present invention is characterized by the camera including:
a correcting optical unit for correcting a camera movement;
a calculation circuit for calculating a drive target value of the above described camera movement correcting optical unit based on a camera movement signal;
a computation circuit for computing a light exposure amount to a storage medium; and
exposure amount control means for, even if the above described drive target value exceeds a drive threshold amount of the above described camera movement correcting optical unit during the exposure operation for the storage medium, continuing exposure to the above described storage medium until it reaches the light exposure amount computed by the above described computation circuit in the case where a difference between the above described drive target value and the above described drive threshold amount is a predetermined amount or less, and on the other hand, stopping light exposure to the above described storage medium in the case where the difference exceeds the above described predetermined amount.
In particular, the above described computation circuit computes an exposure amount based on luminance information of an object, lightness of a photographing optical system and sensitivity of the storage medium.
In addition, the above described the drive threshold amount indicates a mechanical end of the above described correcting optical unit.
In addition, the above described predetermined amount is changed according to a zoom position of the photographing optical system.
In addition, the above described predetermined amount is changed according to a stop value of the photographing optical system.
In addition, the above described exposure amount control means stops the light exposure to the above described storage medium after predetermined time elapses even in the case where the difference exceeds the above described predetermined amount.
Or the camera including:
the correcting optical unit for correcting the camera movement;
the calculation circuit for calculating the drive target value of the above described camera movement correcting optical unit based on the camera movement signal;
the computation circuit for computing the light exposure amount to the storage medium; and
the exposure amount control means for, even if the above described drive target value exceeds the drive threshold amount of the above described camera movement correcting optical unit during the exposure operation for the storage medium, continuing the exposure to the above described storage medium until it reaches the light exposure amount computed by the above described computation circuit in the case where the difference between the above described drive target value and the above described drive threshold amount is the predetermined amount or less, and on the other hand, stopping light exposure to the above described storage medium in the case where the predetermined time elapses after the difference exceeded the predetermined amount.